| A method for compound specific hydrogen isotope analysis of methyl tert-butyl ether (MTBE) was developed and determined to have an accuracy and reproducibility of ±4‰. Carbon and hydrogen isotopic fractionation during aerobic biodegradation of MTBE by PM1 bacteria and microcosms from Vandenberg Air Force Base (VAFB), California was evaluated to determine their relative merits. Reproducible carbon isotopic fractionation exhibited by both consortia suggests it can be used to quantify the extent of MTBE biodegradation at contaminated field sites. Hydrogen isotopic fractionation exhibited by PM1 bacteria was reproducible, whereas considerable variability in the extent of hydrogen enrichment was documented for the VAFB microcosms. For both consortia, hydrogen isotopic fractionation was larger than that of carbon. Hydrogen isotopic exchange does not occur between MTBE and water. As such, the large hydrogen isotopic fractionation documented here suggests that hydrogen isotope analysis offers significant potential as an indicator of in-situ biodegradation. |
